This invention relates to the synthesis of nanocrystalline particles.
Nanocrystalline particles are of wide interest to researchers in various fields because of their properties as well as their many important technology applications. Such nanocrystalline materials show size-dependent characteristics and often possess unique electronic, magnetic, optical, chemical and mechanical properties that cannot be achieved by using their bulk counterparts. Some important nanocrystalline particles are electrochromic materials that change colors under the influence of an applied potential.
Devices using electrochromic materials have traditionally been limited to applications that do not require rapid color changes, such as windows that can be tinted at the flip of a switch. Fast electrochromic materials, such as those reported in this specification, could be a solution for low-cost, low-energy displays. High performance electrochromic devices require fast ionic diffusion, a uniform structure without local defects, and a significant charge modulated optical response (1-4). Numbers in parentheses refer to the references listed herein, the contents of all of which are incorporated herein by reference. Iridium dioxide (IrO2) has shown promising results as an electrochromic material (5); metal oxides electrochromic materials exhibit superb stability of the metal oxides; and iridium oxide has the fastest response times and displays good color contrast (6). Films composed of nanocrystals or nanowires can form a porous structure, supplying numerous diffusion pathways, while maintaining a highly uniform structure at the atomic level. Biological systems can template the growth of nanostructured crystalline inorganic materials (7-10). Particularly, we have previously reported virus-enabled nanoarchitectures for advanced lithium ion batteries using cobalt oxide nanowires (11). The biological systems provide genetic control of the assembled material as well as enabling aqueous synthesis at ambient temperatures. While previous work has relied on chemical oxidizing or reducing agents in the synthesis of virus nanowires, in this specification a new approach, utilizing electrical pulses to oxidize precursors during biologically-directed nanowire assembly, is introduced.